1. Field of the Invention
The present invention relates to a bicycle, particularly to a twin-frame bicycle.
2. Description of the Related Art
Bicycle is a very popular human-powered transportation means. A bicycle is unstable when standing still and must rely on the rider to maintain equilibrium. Upon driving turns, inertia makes the bicycle body keep forwarding along the original direction. If the center of gravity is too high, bicycle speed is too fast or the bicycle turns urgently, even friction force is enough to offer the necessary centripetal force, the centrifugal moment may cause the bicycle body to rotate and overturn.
When a bicycle turns, by inclination of the driver's body and the bicycle body, the reversed moment can be created to reduce the centrifugal moment which may cause the bicycle to overturn outwards. Because of this, bicycle is naturally more stable in motion than tricycle or four-wheeled vehicle. Currently, one kind of dual-riding bicycle of tandem type already exists in the market. The two driver saddles of a tandem bicycle are arranged one after the other instead of side by side. Just like the conventional bicycle, the tandem bicycle must rely on the rider to maintain equilibrium when standing still. Another kind of dual-riding bicycle, of parallel type, also exists. However, the structure of a parallel dual-riding bicycle links two independent bicycles by a fixing rod, which results in awkward action at high speed or when turning. At high speed, sharp turn or bumpy road may cause the parallel dual-riding bicycle to overturn. Thus, it is only good for children learning to walk.
Consequently, there is a need for a twin-frame bicycle to solve the above-mentioned problems.